KB944 pistons

[Wrambler]

I just received word that the KB944 forged pistons are now available. these are suppossed to be for use with 4.0L rods and IIRC hav a 22cc dish.
I have no other information, just a reply to the question of when they would be available

This is what I received today via email

"Bob Borowick" <[email protected]>


To:<[email protected]>
Subject:KB944
Date:Friday, May 23, 2008 3:50:51 PM
[View Source]
KB944's are available now.
Bob Borowick
tech dept

[Wrambler]

this follow up, if someone wants to move this somewhere else please feel free.
Rats, no standard bore.


Hi
We are showing .030", .040",and .060" for the KB944 & KB945. After June 1st
you can get them with rings, just add KTM to the part number to add rings.
For more info go to the links below.
http://www.kb-silvolite.com/forged.php? ... s&P_id=543

http://www.kb-silvolite.com/forged.php? ... s&P_id=542

Try Summit Racing, Speed-O-Motive, Jeg's or any dealer that handles KB &
Silvolite pistons.
Bob Borowick
Tech dept


----- Original Message -----
From: <[email protected]>
To: "Bob Borowick" <[email protected]>
Sent: Friday, May 23, 2008 2:07 PM
Subject: Re: KB944


> Can I get specifics as to available sizes and distributers?
>

[Flash]

This is vary interesting and hopeful
Said,ratio was figured with a .010 below deck and with a .052 head gasket........if this works out to be true, that would make a Quench of .062, for the 9.1 or the 10.1 this would be good, and a .043 gasket would make it even better!!!!!!!!

The only problem i see with there spec. is there calculator for compression. When you input 58 head cc the compression is 9.73 an 10.90............Is it possible, that there measuring on something other then CC (cubic Centimeters)

.053 quench with out haveing to deck the block is good

Using there crank to deck hight and subtracting out half the stroke?????? i came up with .0095(Piston to deck hight) which is vary close to .010" that they said.
So if my math is corect......and i thing it is.

I pulled out my compression calculator and at .010 deck height,58 cc head 3.895 bore and stroke (.020 over bored w 258 crank) and the 9.1KB piston. It came out to be 10.31:1 compression Something still isn't right.


Flash

[John]

I am coming up with problems with their math, not yours, itching to buy a set, but I don't want to until they get straight what they are selling. Brown bag specials, not the way to sell items at that price bracket.
John

[Wrambler]

Here is the respoonse from Summitt this AM.

Response (Zack) 05/24/2008 10:09 AM
Here is a part number and price for .020 over. .060 will be available in the future but not sure when. You can call our sales line at 1-800-230-3030 to place the order. They would need to be ordered. Thanks
UEM-KB944020-6 SET OF 6 PISTONS 478.69

End of Summit message

Not sure what the benefits would be over a set of diamonds bought direct.
I'm not the guy to ask either

If they work out to be a good choice I would probably go with them to help improve the market choices and hopefully show thew the sales potential for the "right" cast piston.
On the bright side I got a lead on a set of 677p's in standard bore.
Talk about a hard to find piston anymore. Bad enough we can't get a true ready to run stroker cast piston for 4.0L rods without them drying up the one that works with 4.2L rods without machining.

At least kb is starting to produce something for off the shelf use.

[Cheromaniac]

I pulled out my compression calculator and at .010 deck height,58 cc head 3.895 bore and stroke (.020 over bored w 258 crank) and the 9.1KB piston. It came out to be 10.31:1 compression Something still isn't right.
Flash

You forgot the head gasket volume. My maths comes as follows:

Displacement = 4563cc
Cylinder volume = 760.5cc

Head chamber volume 57cc + Piston dish volume 22cc + Head gasket volume (Victor 0.043" thickness) 8.9cc + Deck clearance volume 2cc = Total combustion volume of 89.9cc

Compression ratio = (760.5 + 89.9)/89.9 = 9.46:1
With a quench of 0.053" you'd easily be able to run 89 octane but you'd need a cam with at least 204* @ 0.050" intake duration.

[Shark]

is it just me or is this more expensive then you guys imagined these slugs would be?

[Flash]

I pulled out my compression calculator and at .010 deck height,58 cc head 3.895 bore and stroke (.020 over bored w 258 crank) and the 9.1KB piston. It came out to be 10.31:1 compression Something still isn't right.
Flash

You forgot the head gasket volume. My maths comes as follows:

Displacement = 4563cc
Cylinder volume = 760.5cc

Head chamber volume 57cc + Piston dish volume 22cc + Head gasket volume (Victor 0.043" thickness) 8.9cc + Deck clearance volume 2cc = Total combustion volume of 89.9cc

Compression ratio = (760.5 + 89.9)/89.9 = 9.46:1
With a quench of 0.053" you'd easily be able to run 89 octane but you'd need a cam with at least 204* @ 0.050" intake duration.

You are right about the head gasket, i didn't for get the gasket spec...........I just entered .052 for the head gasket bore, instead of 4.00"

OK, with all the info added directly to my calculator the 9.1 piston with a .052" gasket came out to be 9.32 compression with a ,062 quench.
With the same above and a .043" head gasket it was it was 9.40 and a quench of .053

10.1 came out to be 10.25.................
As long as the piston really does sit .010 below the deck............I'm really liking these numbers.

If you shaved .008 of the deck(Making the piston to deck height .002) you would have a perfect quench, at .045" and 9.54 compression.(with the 9.1 KB piston.....)

Dyno, thanks for making me double check my math

[gradon]

The KB piston sits .0295" below deck(not much better than the 4.2 rod/h825cp setup I went with, which is .0385"), unless you have some machining done. I too was expecting them to be in the $300-350 range, especially since you can buy random v8 forged KB sets from summit for $320-450(25% more parts). I'm sure it's a quality piston, but if I was shelling out that much money, I would go with a Diamond/Ross piston which would put it closer to a zero deck with some room to have the block machined. Anyhow the 944s weren't meant to be for me and actually delayed my build because of the run around they kept giving/false info/no info. I could have bought a set of the h802cp20s a month ago and saved money--they cost $10 cheaper than the 825s, but the prem moly metric rings are $30 more than the standard ones. At least I got a set of good pistons--many people are having a hard time.

[Flash]

is it just me or is this more expensive then you guys imagined these slugs would be?

yes,
If they are real close to what a custom piston would be in spec (prefect spec as fare a quench is concerned)
and the compression on target...........they are high but probably worth it..........But they are basicly $80 piston

I have been on the KB sight, scratching my head and punching numbers into a calculator. Trying to figure out how they came up with there numbers!!!!!!!!!

The first thing that isn't right, is the deck height, 9.1 piston has a 9.433 Deck Height, and the 10.1 has a 9.429
NO MATTER WHAT COMPRESSION RATO YOU HAVE, IT WILL NOT AFFECT DECK HEIGHT!!!!!Deck height is set from the factory when the block is Machined. and the only way to change it, is if you have you block DECKED!

DOES ANY ON HAVE THE FACTORY (AMC/CHRY) STOCK DECK HEIGHT SPEC

The piston to deck height spec is different between the two pistons because of the deck height variance(.0195(9.1).015 and they say that both pistons have .010" piston to deck height (which i would have a problem with it it was true!)

All thow i can't prove there numbers, i recalculated there number right down to the stock bore spec that they used.

Bore 3.875 / Stroke 3.975 / 58 cc head / .052"head gasket / 4.00" head gasket bore (10.708 cc) / .010 piston to deck / 21.75 cc or 11.38........
9.1= 9.15 @.062 quench
10.1= 10.18 @ .062

[Cheromaniac]

The KB piston sits .0295" below deck.

You are correct. The info. from KB's site implies that you need to mill 0.020" from the block deck to get a 0.010" deck clearance.

[gradon]

I still haven't wrapped my head around the floating pin concept. I understand their 1.353" compression height if they allowed for the use of the eagle 6.150"rod, which would leave the piston .0045" below deck(my machinist shaved my head the bare minimum .004", so I would've done that as well had I been lucky enough to get the rods off ebay for $200 like someone did). Does anyone know if the eagle rod can be pressed on any 4.0 piston, or does it have to be a floating pin piston? Would/could you have to buy floating pins to put in the KBs?

[John]

Flash the 4.0 deck height is 9.450 to 9.456 inch or for those metric inclined 240.03 to 240.18 mm. Data source Mopar Jeep Engines book 3rd. Edition.The deck height for the 4.2 motor is 9.487 to 9.493 inch or 240.97 to 241.12mm. And implied/inferred doesn't get it in performance. They need to spec. clearly what they are selling . Or hell, should I run out and buy one of those evil bay electric superchargers?
John

[Flash]

Flash the 4.0 deck height is 9.450 to 9.456 inch or for those metric inclined 240.03 to 240.18 mm. Data source Mopar Jeep Engines book 3rd. Edition.The deck height for the 4.2 motor is 9.487 to 9.493 inch or 240.97 to 241.12mm. And implied/inferred doesn't get it in performance. They need to spec. clearly what they are selling . Or hell, should I run out and buy one of those evil bay electric superchargers?
John

Thanks, Mopar Jeep Engines book 3rd. Edition........Good enough

Electric SuperCharger!!!!????????
I have seen a hair dryer installed as a Joke...................
Would be a variable rpm Charger, right? How much boost do they claimer to sustain!

So using the deck height of 9.450
9.1= 8.72 W/.052 head gasket and a quench of .0885
10.1=9.64 " "
With out any mods this is what we get..........less compression for similar quench.
Is the price of this piston worth it?

#1 How much more is a custom piston compared to this one?

#2 How much will it cost for the deck to be cut .031" esh, then you need different push rod Because of the decking for this new piston?

#3 How much would it cost to buy the slvo's, Have it dished to proper cc, and then have it decked to get a good .045-.040 quench height......... and push rod would need to be figured here also.

If your goal is "X" compression with .040 quench...........would the custom piston be cheaper, in the end????????

And i guess there is option 4

#4 Eagle rods with a the 6.150 length and the new KB piston.......................Hmmmm, Well lookie looky, piston to deck is .0095" or .010" if you round it up.......Just what KB said it was.
So this combo would not require new push rods, no shaving of the block,
With a .043 head gasket would make a [9.1 KB] and actual 9.32:1 compression ratio W .0525 Quench!!!!!!!
9.16 with a .052" thick head gasket!!!

So which route would be the cheapest including machine work??????


Flash

[John]

Was building a 401 and looking for 10.25:1 compression ratio, contacted KB people and was told "no problem" at the last minute it was revealed "no problem if you switch to modified Chevy rods. No sale.
John